Quantifying respiratory effort is a key step in physiological and clinical research on exercise tolerance, mechanisms of fatigability, and ventilatory impairment. To date, reliable assessment relies on an invasive method: esophageal pressure (Pes) measurement using a balloon catheter inserted into the esophagus. Although Pes provides an indirect estimate of pleural and intrathoracic pressure, it is uncomfortable for patients, requires dedicated equipment, and may limit study participation.
In critically ill patients, a noninvasive approach to quantify respiratory effort would have major clinical and scientific value. In acute respiratory distress, accurately tracking the intensity and evolution of respiratory effort could support earlier therapeutic decision-making.
Shear Wave Elastography (SWE) is an ultrasound technology enabling very high acquisition rates and estimating tissue stiffness from shear-wave propagation induced by an acoustic impulse. Because muscle stiffness is strongly related to force produced during contraction, we hypothesize that intercostal muscle stiffness measured by SWE correlates with respiratory work and increases with rising inspiratory load.